Originally Posted by andrewclaus

I'll add a tip to make your upcoming inspections easier, but it only works if your cable housing is routed through a slotted frame cable stop. Shift into the largest sprocket (front or back), stop pedaling, then shift into the smallest sprocket position. This will give enough slack to pull the housing out of the frame stop. Squeeze the brake lever to expose the cable entrance hole. Push the cable out of the shifter to inspect for broken strands. This way you can retain all shifting adjustments.

Also, if you find yourself turning a barrel adjuster every few weeks to keep shifting smoothly, that's a sign the cable is fraying.